The process of the release of mature spermatids from Sertoli cells into the lumen of the seminiferous tubule is termed 

Sperm heads that are embedded in the Sertoli cells are finally released from the seminiferous tubules by the process called spermiation.

Insemination is introduction of sperm into the female genital tract.

Ejaculation is the release of  semen (sperm cells and seminal plasma) from the penis.

Spermiogenesis is a process in which spermatids are transformed into the spermatozoa.